Submersible pumping systems are often deployed into wells to recover petroleum fluids from subterranean reservoirs. Typically, the submersible pumping system includes a number of components, including one or more fluid filled electric motors coupled to one or more high performance pumps. Each of the components and sub-components in a submersible pumping system is engineered to withstand the inhospitable downhole environment, which includes wide ranges of temperature, pressure and corrosive well fluids.
Components commonly referred to as “seal sections” protect the electric motors and are typically positioned between the motor and the pump. In this position, the seal section provides several functions, including transmitting torque between the motor and pump, restricting the flow of wellbore fluids into the motor, protecting the motor from axial thrust imparted by the pump, and accommodating the expansion and contraction of motor lubricant as the motor moves through thermal cycles during operation. Many seal sections employ seal bags, labyrinth chambers and other separation mechanism to accommodate the volumetric changes and movement of fluid in the seal section while providing a positive barrier between clean lubricant and contaminated wellbore fluid.
Because most seal sections include one or more rotating shafts that transfer torque from the motor to the pump, the fluid separation mechanisms in the seal section must be configured to accommodate the shaft. In the past, mechanical seals have been placed around the shaft to prevent fluids from migrating along the shaft. Generally, a mechanical seal includes components that provide a structural barrier against fluid migration. A popular design of mechanical seals employs a spring on the exterior of the mechanical seal that exerts axial force on components of the mechanical seal. The spring keeps the components of the mechanical seal in proper position to keep the well bore fluids from migrating along the shaft.
While generally acceptable, prior art mechanical seals may be susceptible to failure in certain environments. As wellbore fluids are drawn into the seal section, sand and other particulate solids may collect in the proximity of the mechanical seal. Contamination with solid particles degrades the performance characteristics of the mechanical seal spring and compromises the sealing surfaces of the mechanical seal, resulting in a failure of the mechanical seal. Accordingly, there exists a need for an improved design that is more resistant to contamination and wear caused by solid particles. It is to this and other deficiencies in the prior art that the embodiments are directed.